1. Field of Invention
This invention relates to a hand-held surgical tool used in microsurgery and, more particularly, to a microinstrument such as a forceps, scissors, needle holder, or the like which can be used with rotational microsurgery techniques.
2. Description of the Prior Art
Of the various types of surgery practiced today, microsurgical techniques are extremely demanding and pose difficulties unique to their field. For example, the size of needles, thread and body parts are microscopically small, and typically, microsurgery is performed under 20.times. magnification. Also, inefficiencies in the manual movement a surgeon is required to perform during an operation become an area of major concern since microsurgery requires very precise, critical movements, and the operations are quite lengthy, typically requiring hundreds if not thousands of distinct hand, wrist and arm movements.
In a broad categorization, two types of techniques, each having their own type of microsurgical instruments, are in use today. In a first category, the tools used in microsurgery are generally scissor-like instruments which have a pair of pivoted levers joined at a common pivot with a handle at one end and a pair of jaws at the other end, and which are opened and closed by moving the handle. Another similar type of hand-held instrument used in microsurgery is of the tweezer or forceps type in which the two deflectable spaced tongs are joined at one end and are brought together at the other end by finger pressure. These types of scissor action instruments are grasped by the surgeon's palm and fingers and are manipulated by turning (pronating and supinating) the surgeon's wrist. Another similar type of tool falling in this category includes flat-handled microsurgery instruments which are held by the tips of the fingers, but still require wrist pronation and supination to turn them.
Turning now to the second general category, rotational microsurgery techniques employ round-handled microsurgical instruments, the type addressed by the present invention, which can be grasped like a pencil and manipulated by rolling the thumb on the middle finger. A particular advantage in using rotational microsurgical techniques is realized since the muscles which control motion at the fingertips are more precise than those muscles which control the wrist, due to the large area of brain devoted to their control. Further, rotational techniques are less tiring, especially during operations of extended duration.
The present invention is directed to instruments of very high precision, much higher than that required for standard surgical instruments. Typically, microsurgery is performed under 20.times. magnification, and accordingly, any misalignment in the microsurgical tool is amplified accordingly. In addition, amplification of certain types of misalignment results from the typical pivotal mating of tool halves. The quality of tools used in microsurgery is also subject to rigorous demands by virtue of the small sizes and delicate composition of the surgical arteries and body parts manipulated by those tools. Blood vessels cut, dilated, grasped and sutured by the instruments are typically in the range of 0.5 mm in diameter. Thread employed in suturing is finer than human hair and is gossamer fine. To the human eye, unaided by magnification, the curved needles are as fine as a baby's eyelash having a diameter of about 70 microns, i.e., 0.070 millimeter. If the microsurgical needle is grasped and is bent by the forceps, then it is no longer useful. Further, the forceps is used to grasp the fine thread to assist in tying knots for a stitch. In other instances, a surgeon will grasp a curved microsurgical needle with a conventional needle holder in his dominant hand and with a forceps in the non-dominant hand he will grip and rotate the needle tip through a 90.degree. arc. He may then release the tip and regrip the needle tip and turn it an additional arc so that the needle is properly oriented with the point up and ready for the rotational and spinning movement. The slightest opening of the tip of a forceps or scissors, for example, would render the tool very difficult, if not impractical for use in a delicate operation, especially operations of extended duration involving many hundreds if not thousands of tool manipulations.
It is easy for these fine needle-pointed tips of the microinstrument to move out of proper mating alignment, i.e., to drift apart, splay, or twist relative to one another between an opened position and a fully closed, tightly gripping position. As a result, the needle, thread, or tissue, for example, are not properly gripped, cut or held as is desired. Because of the microscopic size of needles and sutures and also because of the microscopic size of portions of the body which are being repaired, it is imperative that improved alignment arrangements be provided for forceps, scissors and other hand-held microsurgical tools. Thus, there is a need for a microinstrument which guarantees constant alignment during the full range of opening and closing of the forceps-type device and that, regardless of the position of the instrument and the direction of manipulatory forces being applied to the instrument, the ends will always come together in perfect alignment, and will not move or twist relative to one another.
There is a particular need for a microinstrument having the above improvements which can be rotated easily with finger movement rather than with wrist movement. In particular, the rotational surgical technique presents a somewhat unique problem in providing a proper alignment between tips comprising mating halves that are drawn together by a surgeon's finger pressure. A crossing over of the tips in a direction perpendicular to that of tool closure is much more likely when the rotation surgical technique is employed, since the surgeon is frequently rotating the tool while the two halves are pressed together.
In addition to providing a forceps or gripping type of microsurgical instrument, the present invention is directed to scissors which can be used in microsurgery, particularly the rotational type of microsurgical technique. Such a scissors instrument must be capable of rotation by the microsurgeon to almost any angle in that the surgeon must be able to compress the scissor tips together to form a cut in tissue or thread while at an awkward angle. Because the tips are so finely pointed in a forceps-like scissors, it is difficult to hold the scissor blades close together so that they properly shear through the tissue at such angles. Particularly, when the scissor blades are rotated away from a vertical plane (i.e., by the pronation or supination movements associated with these instruments) before compression toward one another, there is a tendency for scissor blades to twist laterally, a particularly noticeable effect under 20.times. magnification, thereby causing a greater spacing between the shearing edges and a more difficult cut.
As pointed out above, the duration of microsurgery operations is typically quite lengthy, e.g. 20 hours. Hence, the force to open or close the instrument, if properly set, may reduce the amount of hand fatigue. With the present invention, a predetermined biasing force may be provided to bias the tool to open as the surgeon releases his grip on the tips. Preferably, the alignment is continuous throughout the entire opening and closing range of the instrument, and should be as smooth and frictionless as possible. This is in contrast to many of the instruments currently provided to microsurgery practitioners. Typical alignment arrangements used in these instruments include a pilot pin on one part of the forceps which is in alignment with an opening on the opposite side of the forceps. Only when the forceps is in the final stages of closure, will the pin enter the associated opening to maintain alignment of the two sides of the forceps. When the instrument tips are fully open, the alignment pin is out of its associated, spaced opening. If the closing pressures of the surgeon's fingers are not exactly opposite and aligned normal to the longitudinal axis of the instrument, the tips will be out of alignment and the pin can miss the opening, thereby preventing the instrument from closing.
Microsurgical instruments are expensive because of their high precision surfaces and fine tolerances. Any unintentional impact to the tip of the tool is attended by a high probability that the tool will become damaged, perhaps rendering it incapable of further use. Therefore, it is desirable that such tools be capable of interchanging with replacement tips, especially with different tips capable of forming different operations. Thus, the precision of the mating portions comprising a microsurgical tool must be quite high. That is, the configurations of the mating portions must be reproduceable from exchangeable part to exchangeable part. At present, many microsurgical tools are hand made by skilled craftsmen. As has long been apparent in other fields, such handmade tools do not lend themselves to such interchangeability, especially an interchangeability that assures that the new tips have the necessary alignment for gripping microscopically fine microsurgical threads or needles, or for cutting.
Thus, there is a particular need for a cost-effective, accurate and precise, repeatable method of making tools used in microsurgery. Further, to assure commercial success in providing interchangeable parts used throughout the market of surgeons practicing microsurgery, a method for the automated manufacture of replaceable tool parts is needed. In particular, such automated process should ensure the proper mating of forceps and scissors tips, even tips of a very small included angle which have long and slender mating halves.